Electrical switch board



(No Model.)

T. N. YAIL.

ELECTRICAL SWITGH BOARD.

No. 255,056. Patented Mar.14,1882.

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UNITED STATES PATENT OEEICE.

THEODORE N. VAIL, OF BOSTON, MASSACHUSETTS.

ELECTRICAL SWITCH-BOARD.

SPECIFICATION forming part of Letters Patent No. 255,056, dated March 14, 1882,

-Application filed December 14, 1881.

To all whom 'it muy concern Be it known that I, THEO. N. VAIL, of Boston, in the count-y otA Suffolk and State of Massachusetts, have invented certain Improvements in Electrical Switch-Boards, of which the following is a specification.

My invention relates to electrical switchboards of that class wherein the connectionstrips whereby anytwo circuits are united are represented by sheets or plates ot' metal insulated one from another by alternate sheets of vulcanite or other suitable nou-conducting material, while the several line-circuits are attached to and represented by smaller plates, one for each circuit, these latter being secured to the surface of the uppermost or front nonconducting plate. The connections iu such switch-boards are made by thc insertion of plugs made in pairs ot' different lengths, each separate pair ot' plugs being ot' the precise length requisite to make Contact, with one of the connection-plates and with no other, while, irrespective ot'length, all the pairs are adapted to make contact with the smaller or line plate. Such a switchboard has been patented by Francis Blake, No. 249,574,November 15,1881, and reference may be made to that patent, upon which my present invention is an improvement.

For convenience I shall hereinafter term the large metal plates, which are interleaved between the non-conducting plates, connectionplates,7 and the small surmounting -plates line-plates.

It is evident that the switch-board described in the said patent of Francis Blake will perfectly perform all the necessary functions of an electrical commutator with exactness and convenience, so long as the circuits entering therein `and the required circuit-changes are few in number. Experience has, however, demonstrated thatintelephone-exchangeslocated in cities of any importance, or at great centers of population, the number of circuits ot' necessity entering the commutator or switch-board is large, ,and the number ot' changes and connections of such circuits correspondingly so. It has also been determined by actual practice 'that in large telephone-exchanges facilities must be provided for the simultaneous connection ot' at least one-fourth of the entire (No model.)

number of circuits entering the central station, and also that the extent of such facilities must be increased in a greater ratio than the numbgr of line-circuits, for it is apparent that in a telephone-exchange comprising, we will say, live hundred subscribers the addition ot' one subscriber is virtually not only one subscriber added to the exchange, but an addition of one to every one of the tive huudred-thatisI each subscriber ot' the tive hundred has one more to connect with and to converse with, it' he so wishes. In view of these facts it is obvious that a switch-board constructed as above and designed for the reception of a large number of line-circuit plates must have a correspondingly large number of coiinection-plates, and that any considerable increase in the number of connection-plates and the alternating nonconducting plates must tend to the construction of a switch-board ot' extaordinary and unwieldy thickness, requiring for the manipulation of the hindermost plates plugs of great and inconvenient length. If, for example, the board be prepared for the reception ot' the hereinbefore-mentioned number of lines-viz., tive hundred-it will be requisite also to provide onefourth of that number of connectionstrips, which, even if made as thin as one-sixteenth of an inch, will, with the additional thickness of the alternating insulating-plates, produce a total thickness ot' fifteen inches. Increasing the number of subscribers lines to two thousand would produce a switch-board with connecting-plugs ef the maximum length of tive feet. It becomes therefore a desideratum to reduce extremely the thickness of the connection-plates and ot' their interveniuginsulating-plates; but it is found in practice very ditlicult to accomplish this successfully, inasmuch as the connecting part of the plug must be correspondingly diminished longitudiually, or in addition to making the required contact with the proper plate it will contact also with the adjoining plates, or else the said conducting end of the plug must be cut down to a thickness not exceeding that of one of the plates and its two contiguous insulating-plates. Such a construction would not, however, admit of the plug obtaining a sut'ticient purchase to form an electrical connection of any value.

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To construct a switch-board of the general character of the class hereinbefore described, and to provide means whereby the plates may be reduced in thickness to any required degree, while at the same time the excellence of the electrical connection shall be maintained unimpaired, is one of the objects of my present invention. An additional object is by such construction to provide a switch-board and connecting-plugs therefor, which, while of ample capacity for the accommodation of a large number of lines, may at all times be conveniently manipulated. I attain these ends by farming the holes ot each separate connection` plate with a contact-smface upon a portion only of their peril'ihery, and by so arranging the said contact that it shall be at a different portion ofthel periphery ofcontiguous plates; also, by the employment of a connectingplug of special character,which at its inner end is composed of non-conducting material, except atone point, differing in every case from the plugs designed for the conducting contiguous plates oi either side.

It consists also in a special conformation of the connecting-plugs at their upper end and of a similar conformation of the holes through the small line-plates, where they are fitted for the reception of the plugs, and ot' means wherebythe electrical connection between the plugs and the said line-plates is improved and maintained intact.

It consists also in means whereby the insertion ot' the plug breaks the continuity of the normal line-connections to earth, substituting` therefor a connection through the predcter mined connection-plate to the second line required.

In the drawings by which 1 illustrate my invention, Figure l isa section taken on line ze of Fig. 2. Fig. 2 is a plan of a switch-board constructed according` to my invention, showing several plugs inserted therein. Fig. 3 is a section on line @c on, and Fig. 4 a section on line y y, ot' Fig. l. Figs. 5, (i, 7, and 8 are details showing the relative position in contiguous connection-plates ofthe conducting arc or segmental contact-piece b. Figs. 9 and 10 are side views of a long and short plug; and Fig. 1l is plan view, illustrating the method of' automatically removing` the ground-connection.

`I have purposely shown the plates and plugsurfaces in Fig. l greatly magnified in thickness in order to aid in the lucid explanation ot' my invention and the principles therein embodied.

The drawings show a switch-board adapted for the proper accommodation of sixteen linecircuits, but by my invention lines to any num ber may be added without inconvenience.

My invention contemplates the indeiinite multiplication of connecting plates, which would of course be requisite if the number of line-circuits were greatly increased, and to make this multiplication t'easible I construct them of extremely thin metal. I may, for example, use brass or other suitable metal or alloy of the thickness of one sixty-fourth of an inch and correspondingly thin insulating plates or dielectrics. I prefer for this purpose thin sheets of hard rubber, vulcanized fibre, or paraflined paper, such as is ordinarily used in elec trical condensers.

To provide a means of connection, when desired, between any two ot' the line plates, which shall be of high electrical value, l provide a slot in the side of the hole through the -lineplate, or make the hole of someirregular geometrical figure, and form the shoulder or upper part of thc plug, which is designed to tit therein, of similar or corresponding conformation, so that the plug must ot' necessity always be inserted the same v:1y-namely, with its projecting pin or peg on the same. side as the slot or depression in the hole or socket.

This forms an electrical contact between the line-plate and any plug, while the complementary contact between any two plugs and a connecting-plate is made by making` the holes in the said connecting-plate larger than the plug end, and leaving a projecting conductingsegment in each hole of each plate. rl`hiscouducting-segment may bc equal in length to onefourth of the entire circumference of thc hole, or it may be made equal to but one-sixth of the circum I'erence, or to any other suitable portionthereof. Theseperiphericalcontact-pieces, as shown in Figs. 5 to t., arein successivcplates differently placed, soy thatif in the bottom plate the contact-surface is at the front of the hole inthe next conductingplate it will in every hole be located at the back side, in the nextat the right, in the fourth at the left side, after which, it' preferred, it may belocated again at the front, and so on ad libitnm. lhe plug end which is to make contact on these segments l make of suflicientlength to obtain a purchase upon some three or four ot' them; but I surround it with a non-conducting ferrule, except at one point, which is of metal, and which is in permanent connection with the main body of the plurr. Now, as the non-conducting ferrule is presented to the metallic projections ol" every contiguous connectionplate and the metal strip only in contact with its own connection-plate, it is evident that only the designed plate will be connected with the lilleplate into which the plug isinserted, and that any two plugs of equal length inserted will connect any two line-plates together through the same connection-plates, and in so doing will not make contact with any other plate, irrespective of its near proximity.

Referring now to the drawings, the rows ot' small line-plates c c o2 are fixed in any desired or ordinary way upon the uppermost non-con ducting plate, A, which l preferably make thick enough to provide asubstantial base for the said line-plates and their fastenings. Each linc-plate is connected by small wires (not shown) with its special binding-screw Z. The binding-screws in this case are shown in series at the upper part of the board, and the coilnecting-wires may be brought from them to ICO IIO

the line-plates by cutting grooves in the under surface of the upper insulating-plate and depressing them therein.

rThe holes in the Lipper row of line-plates c2 are tive-sided, but rounded at one side, and those in the second row,c,are also ot' peculiar conformation, while those in the two lower rows, c, are circular, butfurnishcd with a slot, t', at one side. The object ot' each of these peculiar eonformations is to make it impossible to fully insert the plug when in any position except that designed for it. Of course in practice it would be undesirable to use more than one shape for the holesin a single board, but any of theforms shown, or any equivalent form, would answer the purpose.

The several connection-plates are shown in Fig'. 1, and are represented by the small tigures 1, 2, 3, et, 5, and 6, while the interleaved noneonducting plates are represented by the letters a, the whole be connected together-by bolts a at each corner or other suitable points. Taper-holes are bored through each line-plate, and extend through all the conducting and non-conducting plates, for the insertion ot' the connecting-plugs, and in each connection-plate the hole is provided with a metallic contactsurt'ace, b', (shown more particularly in the (letail drawings,Figs. 5, 6, 7, and S.) Thiscontact is the only part of the side ofthe hole that comes in contact with an inserted plug, audit may be made of a separate piece ot' metal let into the side of the whole, or may be an integral part of the substance of the plate. It is also essential, as hereinbefore indicated, that the several segmental contacts jutting into the same holes in contiguous plates shall be dit'- t'erently placed as shown in the figures. Fig. 5 being supposed to represent the lowest plate, the projection Z1 therein extends from the t'ront side into the hole I). lu Fig. G, the next plate, it extends from the rear. In Fig. 7, the third plate,itextendsf'rom the lel't side, and in Fig. S, the fourth plate, the projection extends trom the right, after which a Similar series may be recommenced. It isnot, however, necessary that any of the segmental contacts shall take up one-fourth ot' the internal circumference, as they may be made of any suitable number giving sufticint surface for a connection. It will be observed that the internal surface of each segment is eoncaved, so as to tit accurately on and around its corresponding portion ot' the perimeter ot' the plug when inserted.

A separate pair ot' connectingplugs, P, is requisite for each connectingplate, and all of the said plugs are similarly constructed irrespectivc ot' length. Each plug consists ot' a suitable handle, e, a peculiarly formed upper contact-piece, 71 for connection with the lineplate, a comparatively slender shank, and a lower contact piece, j, for connection with the proper connecting-plate. The handle e ot' the plug P is split, and a spring, g, tixed in the crotch f, by which the two sides are ordinarily forced apart, but when the plug is inserted in any hole pressure is brought to bear upon the spring', which is thus maintained tense, and presses the two sides of the plug against the internal surt'aec of the hole and slot ofthe line-plate. This is shown in Fig. 3, which is a sectional plan ot one of the lineplates c.

The lower eontaet-piece,j, which is the more important part ot' the plug, is shown in Figs. 9 and 10, and in cross-section in Fig. 4. It consists ot1 a nucleus ot' metal, j, continued from the main body ot' the plug, surrounded at all points except one with a ferrule or envelope of some hard non-conducting material k, the entire outside surface comprising the metallic segrnentj forming a virtual metallic continuation ofthe body ofthe plug, and the non-conducting envelope c, being nearly ofpert'ect circular forni. The metal partyof the perimeter should preferably extend very slightly beyond the limits of the insulator, to insure a good connection with the corresponding projection b from the internal surt'ace ot' the hole b, as clearly shown in Fig. 4. rllhe stud or pin hat the side of the plug-shoulder is to t into the slot fi, and thus insure the correct insertion of the plug.

It is clearly shown in Fig. 1 that the conductingpartjot'thelong plug P, wheninserted, passes over more than one of the connectingplates, yet only forms contact with its own plate 5, the same result being also shown as accomplished by the short plug, which makes contact only with plate l, although it passes also plate 2.

In practice the plates are muchthinner than shown, and the plug end would pass some three ort'ouroftheconnecting-plates. lhavcchosen, however, this method ot' illustration as showing the several functions with greater elearness. It', as hereinbefore indicated, I choose to employ coi'rnecting-plates ot' the thickness ot' but one sixtyfourth of an inch, this, with a corresponding thickness of insulating-plate, would be but one thirty-second of an inch, and a consecutive series ot' four connecting plates with their interleaved nou-conducting plates would only occupy a space equal in thickness to one-eighth ot' an inch. lt is apparent that this construction is ordinarily impracticable, but by the use of my invention it may readily be accomplished.

Fig. lt shows a series ot line-plates representing line-circuits, each connected by the spring a to a common ground-plate, m, this being connected with the earth at E.

Through a hole, t', in the line-plate c a nonconducting pin, h, slides easily. This projects normally a short distance into the plug-hole, and may be slightly beveled on its upper side, where it so projects. Normally, the line-eircuit, after passing tothe lineplate c, termiA nates through the spring a at the common ground-platem; but when a plug,P, is inserted in the hole, as shown in two ofthelinc-plates, its action will be to sever the line from the ground spring and plate, and to substitute therefor a new terminal or extension through IOD IlO

the connection-plate, and ultimately to the second line. Of course both holes and pegs are suitably tapered for the easy insertion of the plugs, and, as in the patent hereinafter cited, it is obvious that each connecting-plate will have a single pair of plugs, which can be used with no other connecting-plate, and by keeping each pair by itself two line-circuits can readily be connected with one another by inserting any pair of plugs not in use in the hole which passes through the line-plates belonging to the said two line-circuits.

Although l have described the connectingplugs as being made in pairs, to make contact only upon a single plate I may, if I choose, connect any two contiguous plates by a loopwire,including a telephone or battery, and attach, when desired, one incoming line-wire to one piate ofapair and the otherincoining line to the second plate by using for each plate one only of the pair of plugs adapted therefor.

I now claim as my invention and desire to secure by Letters Patent- 1. In an electric switchboard, the combination of the perforated connection-plates, the interleaved insulating-plates, correspondingly perforated, and the switch-plugs, constructed and arranged substantially as described, so that said plugs, when inserted, havea bearing extending over two or more such connectionplates, but in electrical contact only with the desired one of said connection-plates, as set forth.

2. In a series of connecting-plates separated by interleaved insulating-plates and piled one upon another, holes provided with conducting segmental contact-pieces, each ofsaid contacts forming the arc of a circle and so arranged that the contacts in the holes of each plate shall occupy a relatively different position in the said circle to that ofthe segmental contact in the holes of the conducting plate or plates adjacent thereto on either side, for the purpose specified.

3. In a switch-board of the class hereinbefore described, the combination of line-plates having the specially conformed or slotted holes and the connecting-plates having corresponding holes, each provided with a segmental conducting-surface differing in position for each consecutive plate, with the plug-connector, corresponding in shape at its shoulder to the conformation of the line-plate hole, and having its inner extremity adapted to make contact electrically with the desired connecting-plate only at that point of its peripheral surface which, when the plugis properlyinserted, faces thesaid segmental cond ucting-projection of the connecting-plate hole, for the purpose specitied.

4. rIhe hereinbefore-described connectingplu g,adapted byla sl'iecially-conform ed conducting-shoulder to tit and make contact with the line-plate only when properly inserted therein, and by a conducting-strip at one portion of the longitudinal surface of its foot or inner end (all other portions of said surface being insulated) to make a complementary contact to the required connection-plate, and consisting of the said conducting-shoulder, a contact-maintaining device therefor, the said foot or inner extremity, a conducting-shank, electrically connecting the said shoulder with the foot or opposite end, and a handle, substantially as and for the purpose spccilied.

5. 1n a switch-board comprising a series of conducting-plates, each separated from its contiguous conducting-plate by an alternatingsuccession ofnon-conducting plates or diaph ragms, the whole piled one upon another, conductingplates perforated with holes extending through the series and provided with segmental contactpieces, each. of said contacts forming the are of a circle and so arranged that the contacts in the holes of each plate shall occupy a relatively different position in said circle to that of the contact-piece in the holes in the connecting plate or plates adjacent thereto on either side, combined with a connecting-plug having at its inner extremity a conducting-strip opposite the projection in the hole of thc desired connecting-plate, but being at all other points of the longitudinal surface of said inner extremity faced with non-conducting material, whereby contact is made only with the required connecting-plate, the contact-pieces of other contiguous connecting-plates impinging only upon the non-conducting face of the plug end, as described.

G. In a switch-board, the combination, substantially as hereinbefore described, of the connecting-plates, piled alternately with non-conducting plates or dielectrics, and having holes extending through the series fitted with conducting segmental projections, as specitied, the line-circuit plates, each perforated with a hole corresponding to and forming part ofthe holes through the connecting-plates, but spe` cially adapted to fit the shoulder of the plugconnector when properly inserted, and a connecting-plug, constructed asindicated, to make contact when properly placed in the line-plate holeand with thatconnecting-plate only which presents a conductingprojection opposite and on the saine plane as its own conducting-surface.

7. rIhe combination, in a switch-board of the class specified, of the line-plate c, having the specially-conforined hole extending through the same, a circuit-closer, and a connectingplug adapted to tit accurately in the speciallyconform ed hole when prOperLynSerted therein, and by the act of insertion to operate the said circuit-closer and break the continuity of the line, substantially as described.

In testimony whereofI have signed my name to this specification, in the presence of two subscribing witnesses, this 8th day of December, A. D. 1881.

THEO. N. VAlL.

Witnesses:

Trios. D. LocKwooD, Gno. WILLis PIERCE.

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